Luciferases are enzymes that catalyze reactions that emit light. Luciferases are named according to their source organisms such as beetles (firefly) or marine organisms. Examples of bioluminescent marine animals include: Renilla, also known as sea pansies, which belong to a class of coelenterates known as the anthozoans. In addition to Renilla, other representative bioluminescent genera of the class Anthozoa include Cavarnularia, Ptilosarcus, Stylatula, Acanthoptilum, and Parazoanthus. All of these organisms are bioluminescent and emit light as a result of the action of an enzyme (luciferase) on a substrate (luciferin) under appropriate biological conditions.
Different luciferases have different properties with regard to substrate specificity and intensity of light emission and stability of the bioluminescent signal, which is commonly measured by a luminometer. Luciferases are useful as transcriptional reporter genes and in imaging reporter gene expression in living subjects and many other applications in molecular biology.
Certain luciferases, such as those that utilize cypridina luciferin (vargulin) as a substrate, can be useful reporters because of their strong luminescent signal and the fact that they are secreted in the native form. However cypridina luciferin (vargulin) is very difficult to synthesize (usually involving an 18-step chemical synthesis). The limiting supply and the cost of the material have made the assay difficult to commercialize.